The aluminum industry generally employs the Hall-Heroult process (U.S. Pat. No. 5,961,811) for producing aluminum. However, carbon cathodes which are traditionally used in the Hall-Heroult cells have the problem that they are not readily wettable with molten aluminum. Thus, conductivity through the surface of the cathode is not uniform but tends to be intermittent. The carbon cathode surface also reacts with the molten aluminum to form aluminum carbide. This reaction depletes the cathode at a rate of 2 to 5 cm/yr for an operating electrolytic cell. This depletion is fostered by the presence of sludge-containing fluoride bath components at the interface between cathode carbon and metal. The presence of aluminum carbide is also detrimental because it results in a high electrical resistivity material which interferes with the efficiency of the cell.
Carbon cathodes also have other problems. The presence of sodium in the electrolytic cell results in the formation of sodium cyanide in the carbon bodies causing disposal problems with the spent potlinings. The Environmental Protection Agency (EPA) has listed spent potlinings as a hazardous material because they contain cyanide.
For at least the reasons discussed above, improved cathodes are needed that are suitable for use in electrolytic cells for producing aluminum. Cathodes that are wettable by aluminum are needed. Economic compositions and methods for fabricating wettable cathodes (in situ) are needed. The compositions and methods disclosed herein address these needs.